1. Technical Field
The present invention relates to an electrolyte solution for hydrogen generating apparatus and a hydrogen generating apparatus including the electrolyte solution.
2. Description of the Related Art
A fuel cell refers to an energy conversion apparatus that directly converts oxygen in the air and hydrogen (which can be obtained from pure hydrogen or hydrogen contained in hydrocarbons such as methanol or natural gas) into electrical energy by an electrochemical reaction.
FIG. 1 illustrates the basic operational principle of a fuel cell. Referring to FIG. 1, a fuel cell 10 may include a fuel electrode 11 as an anode and an air electrode 13 as a cathode. The fuel electrode 11 receives hydrogen molecular (H2). The hydrogen is dissociated at the fuel electrode to form hydrogen ions (H+) and electrons (e−).
The hydrogen ions (H+) move toward the air electrode 13 via a membrane 12 which is an electrolyte layer. The electrons move through an external circuit 14 to generate an electric current. The hydrogen ions and the electrons are combined with oxygen from the air at the air electrode 13 to generate water. The fuel electrode 11 and the air electrode 13 are disposed in between the electrolyte membrane to form a membrane electrode assembly (MEA).
The following Reaction Scheme 1 explains the above mentioned chemical reactions:Fuel electrode 11: H2→2H++2e−Air electrode 13: ½ O2+2H++2e−→H2OOverall reaction: H2+½ O2→H2O  [Reaction Scheme 1]
In short, the fuel cell 10 functions as a battery since the electrons dissociated from the fuel electrode 11 generate current, moving through the external circuit. Such a fuel cell 10 not only is a pollution-free power because it has no noxious emissions such as SOx, NOx, etc., but also produces a small amount of carbon dioxide. Also, the fuel cell device has some advantages, such as low noise and vibration-free and so on.
In order to obtain a high-performance fuel cell, hydrogen may be used as the fuel. In particular, a micro fuel cell may advantageously be applied as a power source in portable electronic devices, such as cell phones and laptop computers, etc. A type of fuel cell suitable for the micro fuel cell is a polymer electrolyte membrane fuel cell (PEMFC), which operates at a relatively low temperature and has a high output density, and which is being thus actively developed.
Meanwhile, stable hydrogen production and supply thereof is the most challenging technical problem to be solved so as to commercialize the fuel cells. A hydrogen storage tank, generally known as the hydrogen generating apparatus, has been used to solve these problems. However, the tank occupies a large space and should be kept with special care.
In order to avoid such drawbacks associated with the known apparatus, fuels such as methanol and formic acid, permitted to be brought into an airplane by International Civil Aviation Organization (ICAO), are reformatted into hydrogen; methanol, ethanol, or formic acid is directly used as a fuel in the fuel cell.
However, the former case requires a high reforming temperature and a complicate system, consumes driving power, and contains impurities (CO2, CO) besides pure hydrogen molecules. The latter case deteriorates power density due to a low rate of a chemical reaction at the anode and a cross-over of hydrocarbons through the membrane.
Besides, hydrogen generating methods for PEMFC are as follows: oxidation of aluminum, hydrolysis of metal borohydride (BH4), reaction on a metal electrode and so on. Among them, the preferable method for efficiently controlling a generation rate of hydrogen is by using the metal electrode.
However, a hydrogen gas flow rate rapidly increases and thus causes water inside a reactor to overflow when the reaction on the metal electrode is carried out continuously. Further, a metal hydroxide is produced as a by-product which exists in a slurry state in a reactor due to its low water solubility and may deteriorate the hydrogen generation efficiency.
Thus, the need is increasing for a hydrogen generating apparatus, which can resolve the problems in generating hydrogen using the metal electrode and generate hydrogen efficiently.